ocaml-batteries-team/batteries-included — pull request #504 by c-cube (2014-01-09 17:04:48+00:00)
Title: Set.Make2 for functorial cartesian product

See #441. I had to build all three sets (domains and product) because otherwise the abstraction barrier would become unbreakable (product on abstract set implementation is better solved using `Enum`, I believe).